"This is a tragic loss for the Zoo Atlanta family - especially so because it was extremely sudden. Mona had shown no signs of illness or distress prior to her abrupt collapse," said the zoo's deputy director, Dr. Dwight Lawson. "The Animal Management and Veterinary teams are currently working to identify any potential condition or circumstance which may have contributed to her death."

A necropsy has been scheduled for Thursday through the zoo's partnership with the University of Georgia's Zoo and Exotic Animal Pathology Service in the College of Veterinary Medicine.

Mona was born in November 2005 at Disney's Animal Kingdom. She and her 6-year-old half-sister Glenda moved to Zoo Atlanta in October 2007. She was the mother of Lily, born in July 2011 at Zoo Atlanta.